diff --git a/types/index.d.ts b/types/index.d.ts
index 1a77877..f9762b7 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -30,6 +30,7 @@ declare namespace express_prom_bundle {
 
     metricType?: 'summary' | 'histogram';
     metricsPath?: string;
+    httpDurationMetricName?: string;
     promClient?: { collectDefaultMetrics?: DefaultMetricsCollectorConfiguration };
     normalizePath?: NormalizePathEntry[] | NormalizePathFn;
     formatStatusCode?: NormalizeStatusCodeFn;